// 顶点着色器
varying vec2 vUv;
void main(){
    vec4 viewPosition = viewMatrix * modelMatrix *vec4(position,1.0);
    gl_Position = projectionMatrix * viewPosition;
    // 设置点的大小,不设置看不见点
    gl_PointSize = abs(20.0- gl_Position.z / 10.0);
    vUv = uv;
}